Contract Address Details

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import "@openzeppelin/contracts/access/Ownable2Step.sol";
import "@openzeppelin/contracts/utils/ReentrancyGuard.sol";
import "@openzeppelin/contracts/utils/Pausable.sol";

/**
 * @title DistributionVault
 * @notice Holds DaiX tokens and distributes them to users at milestone claims.
 *
 * ARCHITECTURE:
 * ┌──────────────────────────────────────────────────────────────────┐
 * │  FUNDING (owner → vault):                                       │
 * │    1. Owner calls fund(amount) — transfers DaiX into vault      │
 * │    2. OR: Owner sends DaiX via standard ERC-20 transfer()       │
 * │    3. getDistributableBalance() returns available for distros    │
 * │                                                                  │
 * │  DISTRIBUTION (vault → users, backend-triggered):               │
 * │    1. User claims via POST /api/distributions/claim             │
 * │    2. Backend calls distribute(recipient, amount) via signer    │
 * │    3. DaiX transferred from vault to user's PulseChain wallet   │
 * │                                                                  │
 * │  FREEZE PROTECTION:                                              │
 * │    - pause(): halts all distributions instantly (owner only)     │
 * │    - proposeEmergencyWithdraw(): starts 7-day timelock           │
 * │    - executeEmergencyWithdraw(): after 7 days, recovers tokens  │
 * │    - cancelEmergencyWithdraw(): cancels if resolved             │
 * │    - Tokens can NEVER be permanently frozen                     │
 * └──────────────────────────────────────────────────────────────────┘
 *
 * ROLES:
 *   owner        — Can fund, pause, set signer, propose emergency withdraw
 *   signer       — Can call distribute() (hot wallet, backend-controlled)
 *   owner2Step   — Ownership transfer requires new owner to accept
 *
 * INVARIANT: totalDistributed <= totalFunded (enforced on-chain)
 *
 * AUDIT: Independently audited April 2026. All critical/high findings resolved.
 * Audit report: https://provedaix.com/audit
 */
contract DistributionVault is Ownable2Step, ReentrancyGuard, Pausable {
    using SafeERC20 for IERC20;

    // ── State ──
    IERC20 public immutable daixToken;
    address public signer;

    uint256 public totalFunded;
    uint256 public totalDistributed;
    uint256 public totalDistributions;

    // ── Per-tx safety limit ──
    uint256 public maxDistributionPerTx = 1_000_000 * 1e18;  // 1M DaiX per claim

    // ── Rolling 24h distribution limit ──
    uint256 public dailyDistributionTotal;
    uint256 public maxDailyDistribution = 10_000_000 * 1e18;  // 10M DaiX/day
    uint256 public rollingWindowStart;
    uint256 public constant ROLLING_WINDOW = 24 hours;

    // ── Dedup ──
    mapping(bytes32 => bool) public processedClaims;

    // ── Signer change timelock (FIX DV-1: 7 days) ──
    address public pendingSigner;
    uint256 public signerChangeTimestamp;
    uint256 public constant SIGNER_TIMELOCK = 7 days;
    bool public signerChangeProposed;

    // ── Emergency withdraw timelock ──
    address public emergencyWithdrawTo;
    uint256 public emergencyWithdrawTimestamp;
    uint256 public constant EMERGENCY_TIMELOCK = 7 days;
    bool public emergencyProposed;

    // ── Reconcile cap (prevents inflation via direct token transfers) ──
    uint256 public maxReconcileAmount = 10_000_000 * 1e18;

    // ── FIX DV-3: Prevent funding/distributing after emergency withdraw ──
    bool public emergencyWithdrawn;

    // ── FIX DV-2: Claim expiry ──
    uint256 public claimExpiryDuration = 90 days;

    // ── Events ──
    event Funded(address indexed funder, uint256 amount, uint256 newTotalFunded);
    event Distributed(
        address indexed recipient,
        uint256 amount,
        bytes32 indexed claimId,
        uint256 timestamp
    );
    event SignerChangeProposed(address indexed newSigner, uint256 executeAfter);
    event SignerChangeExecuted(address indexed oldSigner, address indexed newSigner);
    event SignerChangeCancelled();
    event MaxDistributionUpdated(uint256 perTx, uint256 daily);
    event EmergencyWithdrawProposed(address indexed to, uint256 executeAfter);
    event EmergencyWithdrawExecuted(address indexed to, uint256 amount);
    event EmergencyWithdrawCancelled();
    event MerkleRootCommitted(uint256 indexed epoch, bytes32 root, uint256 timestamp);

    // ── Merkle Root Commitment (FIX XC-1) ──
    mapping(uint256 => bytes32) public distributionMerkleRoots;
    uint256 public latestMerkleEpoch;

    // ── Modifiers ──
    modifier onlySigner() {
        require(msg.sender == signer, "Only signer can distribute");
        _;
    }

    // ── Constructor ──
    constructor(address _daixToken, address _signer) Ownable(msg.sender) {
        require(_daixToken != address(0), "Invalid DaiX token address");
        require(_signer != address(0), "Invalid signer address");
        daixToken = IERC20(_daixToken);
        signer = _signer;
        rollingWindowStart = block.timestamp;
    }

    // ══════════════════════════════════════════════
    // FUNDING
    // ══════════════════════════════════════════════

    /**
     * @notice Deposit DaiX tokens into the vault for future distribution.
     * @dev Requires prior ERC-20 approval: daixToken.approve(vault, amount).
     */
    function fund(uint256 amount) external nonReentrant {
        require(!emergencyWithdrawn, "Vault permanently closed after emergency withdraw");
        require(amount > 0, "Amount must be > 0");
        daixToken.safeTransferFrom(msg.sender, address(this), amount);
        totalFunded += amount;
        emit Funded(msg.sender, amount, totalFunded);
    }

    /**
     * @notice How many DaiX tokens are available for distribution right now.
     */
    function getDistributableBalance() external view returns (uint256) {
        uint256 accounting = totalFunded - totalDistributed;
        uint256 actual = daixToken.balanceOf(address(this));
        return accounting < actual ? accounting : actual;
    }

    // ══════════════════════════════════════════════
    // DISTRIBUTION
    // ══════════════════════════════════════════════

    /**
     * @notice Distribute DaiX to a user for a specific claim.
     * @param recipient  User's PulseChain wallet address
     * @param amount     DaiX amount in wei (18 decimals)
     * @param claimId    Unique claim identifier (prevents double-distribution)
     * @param claimTimestamp  When the claim was originally created (FIX DV-2: expiry check)
     */
    function distribute(
        address recipient,
        uint256 amount,
        bytes32 claimId,
        uint256 claimTimestamp
    ) external onlySigner nonReentrant whenNotPaused {
        require(!emergencyWithdrawn, "Vault permanently closed after emergency withdraw");
        require(recipient != address(0), "Invalid recipient");
        require(amount > 0, "Amount must be > 0");
        require(!processedClaims[claimId], "Claim already processed");

        // FIX DV-2: Reject stale claims
        require(claimTimestamp > 0, "Invalid claim timestamp");
        require(block.timestamp - claimTimestamp <= claimExpiryDuration, "Claim expired");

        // Per-tx safety limit
        require(amount <= maxDistributionPerTx, "Exceeds per-tx distribution limit");

        // Rolling 24h circuit breaker
        if (block.timestamp >= rollingWindowStart + ROLLING_WINDOW) {
            dailyDistributionTotal = 0;
            rollingWindowStart = block.timestamp;
        }
        require(
            dailyDistributionTotal + amount <= maxDailyDistribution,
            "24h distribution limit reached - try again later"
        );

        // Accounting check
        require(totalDistributed + amount <= totalFunded, "Insufficient vault balance (accounting)");
        require(daixToken.balanceOf(address(this)) >= amount, "Insufficient vault balance (actual)");

        // CEI pattern — mark processed BEFORE transfer
        processedClaims[claimId] = true;
        totalDistributed += amount;
        dailyDistributionTotal += amount;
        totalDistributions++;

        daixToken.safeTransfer(recipient, amount);
        emit Distributed(recipient, amount, claimId, block.timestamp);
    }

    // ══════════════════════════════════════════════
    // ADMIN — Configuration
    // ══════════════════════════════════════════════

    /// @notice Propose signer change (7-day timelock — FIX DV-1)
    function proposeSigner(address _signer) external onlyOwner {
        require(_signer != address(0), "Invalid signer");
        pendingSigner = _signer;
        signerChangeTimestamp = block.timestamp + SIGNER_TIMELOCK;
        signerChangeProposed = true;
        emit SignerChangeProposed(_signer, signerChangeTimestamp);
    }

    function executeSigner() external onlyOwner {
        require(signerChangeProposed, "No signer change proposed");
        require(block.timestamp >= signerChangeTimestamp, "Signer timelock not expired");
        address oldSigner = signer;
        signer = pendingSigner;
        signerChangeProposed = false;
        pendingSigner = address(0);
        signerChangeTimestamp = 0;
        emit SignerChangeExecuted(oldSigner, signer);
    }

    function cancelSigner() external onlyOwner {
        require(signerChangeProposed, "No signer change to cancel");
        signerChangeProposed = false;
        pendingSigner = address(0);
        signerChangeTimestamp = 0;
        emit SignerChangeCancelled();
    }

    function setDistributionLimits(uint256 _perTx, uint256 _daily) external onlyOwner {
        require(_perTx > 0 && _daily > 0 && _daily >= _perTx, "Invalid limits");
        maxDistributionPerTx = _perTx;
        maxDailyDistribution = _daily;
        emit MaxDistributionUpdated(_perTx, _daily);
    }

    function pause() external onlyOwner { _pause(); }

    /// @notice Resume distributions — FIX DV-4: resets rolling window on unpause
    function unpause() external onlyOwner {
        dailyDistributionTotal = 0;
        rollingWindowStart = block.timestamp;
        _unpause();
    }

    /// @notice FIX DV-2: Update claim expiry duration
    function setClaimExpiryDuration(uint256 _duration) external onlyOwner {
        require(_duration >= 7 days, "Minimum 7 days");
        require(_duration <= 365 days, "Maximum 1 year");
        claimExpiryDuration = _duration;
    }

    // ══════════════════════════════════════════════
    // EMERGENCY WITHDRAW — 7-day timelocked recovery
    // ══════════════════════════════════════════════

    function proposeEmergencyWithdraw(address to) external onlyOwner {
        require(to != address(0), "Invalid destination");
        emergencyWithdrawTo = to;
        emergencyWithdrawTimestamp = block.timestamp + EMERGENCY_TIMELOCK;
        emergencyProposed = true;
        emit EmergencyWithdrawProposed(to, emergencyWithdrawTimestamp);
    }

    /// @notice FIX DV-3: Sets emergencyWithdrawn — vault permanently closed after this
    function executeEmergencyWithdraw() external onlyOwner nonReentrant {
        require(emergencyProposed, "No emergency withdrawal proposed");
        require(block.timestamp >= emergencyWithdrawTimestamp, "Timelock not expired");
        uint256 balance = daixToken.balanceOf(address(this));
        require(balance > 0, "No tokens to withdraw");
        address to = emergencyWithdrawTo;
        emergencyProposed = false;
        emergencyWithdrawTo = address(0);
        emergencyWithdrawTimestamp = 0;
        emergencyWithdrawn = true;
        daixToken.safeTransfer(to, balance);
        emit EmergencyWithdrawExecuted(to, balance);
    }

    function cancelEmergencyWithdraw() external onlyOwner {
        require(emergencyProposed, "No emergency withdrawal to cancel");
        emergencyProposed = false;
        emergencyWithdrawTo = address(0);
        emergencyWithdrawTimestamp = 0;
        emit EmergencyWithdrawCancelled();
    }

    // ══════════════════════════════════════════════
    // VIEW HELPERS
    // ══════════════════════════════════════════════

    function isClaimProcessed(bytes32 claimId) external view returns (bool) {
        return processedClaims[claimId];
    }

    function getVaultStats() external view returns (
        uint256 _totalFunded,
        uint256 _totalDistributed,
        uint256 _distributableBalance,
        uint256 _totalDistributions,
        uint256 _dailyDistributionTotal,
        bool _paused,
        bool _emergencyProposed,
        bool _signerChangeProposed
    ) {
        uint256 accounting = totalFunded - totalDistributed;
        uint256 actual = daixToken.balanceOf(address(this));
        return (
            totalFunded,
            totalDistributed,
            accounting < actual ? accounting : actual,
            totalDistributions,
            dailyDistributionTotal,
            paused(),
            emergencyProposed,
            signerChangeProposed
        );
    }

    /// @notice Reconcile accounting for tokens sent via direct transfer()
    function reconcileBalance() external onlyOwner {
        uint256 actual = daixToken.balanceOf(address(this));
        uint256 expectedUnused = totalFunded - totalDistributed;
        if (actual > expectedUnused) {
            uint256 extra = actual - expectedUnused;
            require(extra <= maxReconcileAmount, "Reconcile exceeds cap - use fund() for large deposits");
            totalFunded += extra;
            emit Funded(address(0), extra, totalFunded);
        }
    }

    function setMaxReconcileAmount(uint256 _maxReconcile) external onlyOwner {
        require(_maxReconcile > 0, "Must be > 0");
        maxReconcileAmount = _maxReconcile;
    }

    // ══════════════════════════════════════════════
    // FIX XC-1: MERKLE ROOT COMMITMENT
    // ══════════════════════════════════════════════

    /// @notice Commit a Merkle root of sacrifice-to-distribution mappings
    function commitMerkleRoot(uint256 epoch, bytes32 root) external onlyOwner {
        require(epoch > latestMerkleEpoch, "Epoch must be newer than latest");
        require(root != bytes32(0), "Root cannot be zero");
        distributionMerkleRoots[epoch] = root;
        latestMerkleEpoch = epoch;
        emit MerkleRootCommitted(epoch, root, block.timestamp);
    }

    /// @notice Verify a user's distribution against a committed Merkle root
    function verifyDistribution(
        uint256 epoch,
        bytes32 leaf,
        bytes32[] calldata proof
    ) external view returns (bool) {
        bytes32 root = distributionMerkleRoots[epoch];
        require(root != bytes32(0), "No root committed for this epoch");
        bytes32 computedHash = leaf;
        for (uint256 i = 0; i < proof.length; i++) {
            bytes32 proofElement = proof[i];
            if (computedHash <= proofElement) {
                computedHash = keccak256(abi.encodePacked(computedHash, proofElement));
            } else {
                computedHash = keccak256(abi.encodePacked(proofElement, computedHash));
            }
        }
        return computedHash == root;
    }
}
        

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.4.0) (utils/introspection/IERC165.sol)

pragma solidity >=0.4.16;

/**
 * @dev Interface of the ERC-165 standard, as defined in the
 * https://eips.ethereum.org/EIPS/eip-165[ERC].
 *
 * Implementers can declare support of contract interfaces, which can then be
 * queried by others ({ERC165Checker}).
 *
 * For an implementation, see {ERC165}.
 */
interface IERC165 {
    /**
     * @dev Returns true if this contract implements the interface defined by
     * `interfaceId`. See the corresponding
     * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[ERC section]
     * to learn more about how these ids are created.
     *
     * This function call must use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}
          

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.1.0) (utils/StorageSlot.sol)
// This file was procedurally generated from scripts/generate/templates/StorageSlot.js.

pragma solidity ^0.8.20;

/**
 * @dev Library for reading and writing primitive types to specific storage slots.
 *
 * Storage slots are often used to avoid storage conflict when dealing with upgradeable contracts.
 * This library helps with reading and writing to such slots without the need for inline assembly.
 *
 * The functions in this library return Slot structs that contain a `value` member that can be used to read or write.
 *
 * Example usage to set ERC-1967 implementation slot:
 * ```solidity
 * contract ERC1967 {
 *     // Define the slot. Alternatively, use the SlotDerivation library to derive the slot.
 *     bytes32 internal constant _IMPLEMENTATION_SLOT = 0x360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc;
 *
 *     function _getImplementation() internal view returns (address) {
 *         return StorageSlot.getAddressSlot(_IMPLEMENTATION_SLOT).value;
 *     }
 *
 *     function _setImplementation(address newImplementation) internal {
 *         require(newImplementation.code.length > 0);
 *         StorageSlot.getAddressSlot(_IMPLEMENTATION_SLOT).value = newImplementation;
 *     }
 * }
 * ```
 *
 * TIP: Consider using this library along with {SlotDerivation}.
 */
library StorageSlot {
    struct AddressSlot {
        address value;
    }

    struct BooleanSlot {
        bool value;
    }

    struct Bytes32Slot {
        bytes32 value;
    }

    struct Uint256Slot {
        uint256 value;
    }

    struct Int256Slot {
        int256 value;
    }

    struct StringSlot {
        string value;
    }

    struct BytesSlot {
        bytes value;
    }

    /**
     * @dev Returns an `AddressSlot` with member `value` located at `slot`.
     */
    function getAddressSlot(bytes32 slot) internal pure returns (AddressSlot storage r) {
        assembly ("memory-safe") {
            r.slot := slot
        }
    }

    /**
     * @dev Returns a `BooleanSlot` with member `value` located at `slot`.
     */
    function getBooleanSlot(bytes32 slot) internal pure returns (BooleanSlot storage r) {
        assembly ("memory-safe") {
            r.slot := slot
        }
    }

    /**
     * @dev Returns a `Bytes32Slot` with member `value` located at `slot`.
     */
    function getBytes32Slot(bytes32 slot) internal pure returns (Bytes32Slot storage r) {
        assembly ("memory-safe") {
            r.slot := slot
        }
    }

    /**
     * @dev Returns a `Uint256Slot` with member `value` located at `slot`.
     */
    function getUint256Slot(bytes32 slot) internal pure returns (Uint256Slot storage r) {
        assembly ("memory-safe") {
            r.slot := slot
        }
    }

    /**
     * @dev Returns a `Int256Slot` with member `value` located at `slot`.
     */
    function getInt256Slot(bytes32 slot) internal pure returns (Int256Slot storage r) {
        assembly ("memory-safe") {
            r.slot := slot
        }
    }

    /**
     * @dev Returns a `StringSlot` with member `value` located at `slot`.
     */
    function getStringSlot(bytes32 slot) internal pure returns (StringSlot storage r) {
        assembly ("memory-safe") {
            r.slot := slot
        }
    }

    /**
     * @dev Returns an `StringSlot` representation of the string storage pointer `store`.
     */
    function getStringSlot(string storage store) internal pure returns (StringSlot storage r) {
        assembly ("memory-safe") {
            r.slot := store.slot
        }
    }

    /**
     * @dev Returns a `BytesSlot` with member `value` located at `slot`.
     */
    function getBytesSlot(bytes32 slot) internal pure returns (BytesSlot storage r) {
        assembly ("memory-safe") {
            r.slot := slot
        }
    }

    /**
     * @dev Returns an `BytesSlot` representation of the bytes storage pointer `store`.
     */
    function getBytesSlot(bytes storage store) internal pure returns (BytesSlot storage r) {
        assembly ("memory-safe") {
            r.slot := store.slot
        }
    }
}
          

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.5.0) (utils/ReentrancyGuard.sol)

pragma solidity ^0.8.20;

import {StorageSlot} from "./StorageSlot.sol";

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If EIP-1153 (transient storage) is available on the chain you're deploying at,
 * consider using {ReentrancyGuardTransient} instead.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 *
 * IMPORTANT: Deprecated. This storage-based reentrancy guard will be removed and replaced
 * by the {ReentrancyGuardTransient} variant in v6.0.
 *
 * @custom:stateless
 */
abstract contract ReentrancyGuard {
    using StorageSlot for bytes32;

    // keccak256(abi.encode(uint256(keccak256("openzeppelin.storage.ReentrancyGuard")) - 1)) & ~bytes32(uint256(0xff))
    bytes32 private constant REENTRANCY_GUARD_STORAGE =
        0x9b779b17422d0df92223018b32b4d1fa46e071723d6817e2486d003becc55f00;

    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant NOT_ENTERED = 1;
    uint256 private constant ENTERED = 2;

    /**
     * @dev Unauthorized reentrant call.
     */
    error ReentrancyGuardReentrantCall();

    constructor() {
        _reentrancyGuardStorageSlot().getUint256Slot().value = NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and making it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        _nonReentrantBefore();
        _;
        _nonReentrantAfter();
    }

    /**
     * @dev A `view` only version of {nonReentrant}. Use to block view functions
     * from being called, preventing reading from inconsistent contract state.
     *
     * CAUTION: This is a "view" modifier and does not change the reentrancy
     * status. Use it only on view functions. For payable or non-payable functions,
     * use the standard {nonReentrant} modifier instead.
     */
    modifier nonReentrantView() {
        _nonReentrantBeforeView();
        _;
    }

    function _nonReentrantBeforeView() private view {
        if (_reentrancyGuardEntered()) {
            revert ReentrancyGuardReentrantCall();
        }
    }

    function _nonReentrantBefore() private {
        // On the first call to nonReentrant, _status will be NOT_ENTERED
        _nonReentrantBeforeView();

        // Any calls to nonReentrant after this point will fail
        _reentrancyGuardStorageSlot().getUint256Slot().value = ENTERED;
    }

    function _nonReentrantAfter() private {
        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _reentrancyGuardStorageSlot().getUint256Slot().value = NOT_ENTERED;
    }

    /**
     * @dev Returns true if the reentrancy guard is currently set to "entered", which indicates there is a
     * `nonReentrant` function in the call stack.
     */
    function _reentrancyGuardEntered() internal view returns (bool) {
        return _reentrancyGuardStorageSlot().getUint256Slot().value == ENTERED;
    }

    function _reentrancyGuardStorageSlot() internal pure virtual returns (bytes32) {
        return REENTRANCY_GUARD_STORAGE;
    }
}
          

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.3.0) (utils/Pausable.sol)

pragma solidity ^0.8.20;

import {Context} from "../utils/Context.sol";

/**
 * @dev Contract module which allows children to implement an emergency stop
 * mechanism that can be triggered by an authorized account.
 *
 * This module is used through inheritance. It will make available the
 * modifiers `whenNotPaused` and `whenPaused`, which can be applied to
 * the functions of your contract. Note that they will not be pausable by
 * simply including this module, only once the modifiers are put in place.
 */
abstract contract Pausable is Context {
    bool private _paused;

    /**
     * @dev Emitted when the pause is triggered by `account`.
     */
    event Paused(address account);

    /**
     * @dev Emitted when the pause is lifted by `account`.
     */
    event Unpaused(address account);

    /**
     * @dev The operation failed because the contract is paused.
     */
    error EnforcedPause();

    /**
     * @dev The operation failed because the contract is not paused.
     */
    error ExpectedPause();

    /**
     * @dev Modifier to make a function callable only when the contract is not paused.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    modifier whenNotPaused() {
        _requireNotPaused();
        _;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is paused.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    modifier whenPaused() {
        _requirePaused();
        _;
    }

    /**
     * @dev Returns true if the contract is paused, and false otherwise.
     */
    function paused() public view virtual returns (bool) {
        return _paused;
    }

    /**
     * @dev Throws if the contract is paused.
     */
    function _requireNotPaused() internal view virtual {
        if (paused()) {
            revert EnforcedPause();
        }
    }

    /**
     * @dev Throws if the contract is not paused.
     */
    function _requirePaused() internal view virtual {
        if (!paused()) {
            revert ExpectedPause();
        }
    }

    /**
     * @dev Triggers stopped state.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    function _pause() internal virtual whenNotPaused {
        _paused = true;
        emit Paused(_msgSender());
    }

    /**
     * @dev Returns to normal state.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    function _unpause() internal virtual whenPaused {
        _paused = false;
        emit Unpaused(_msgSender());
    }
}
          

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.0.1) (utils/Context.sol)

pragma solidity ^0.8.20;

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }

    function _contextSuffixLength() internal view virtual returns (uint256) {
        return 0;
    }
}
          

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.5.0) (token/ERC20/utils/SafeERC20.sol)

pragma solidity ^0.8.20;

import {IERC20} from "../IERC20.sol";
import {IERC1363} from "../../../interfaces/IERC1363.sol";

/**
 * @title SafeERC20
 * @dev Wrappers around ERC-20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    /**
     * @dev An operation with an ERC-20 token failed.
     */
    error SafeERC20FailedOperation(address token);

    /**
     * @dev Indicates a failed `decreaseAllowance` request.
     */
    error SafeERC20FailedDecreaseAllowance(address spender, uint256 currentAllowance, uint256 requestedDecrease);

    /**
     * @dev Transfer `value` amount of `token` from the calling contract to `to`. If `token` returns no value,
     * non-reverting calls are assumed to be successful.
     */
    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        if (!_safeTransfer(token, to, value, true)) {
            revert SafeERC20FailedOperation(address(token));
        }
    }

    /**
     * @dev Transfer `value` amount of `token` from `from` to `to`, spending the approval given by `from` to the
     * calling contract. If `token` returns no value, non-reverting calls are assumed to be successful.
     */
    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
        if (!_safeTransferFrom(token, from, to, value, true)) {
            revert SafeERC20FailedOperation(address(token));
        }
    }

    /**
     * @dev Variant of {safeTransfer} that returns a bool instead of reverting if the operation is not successful.
     */
    function trySafeTransfer(IERC20 token, address to, uint256 value) internal returns (bool) {
        return _safeTransfer(token, to, value, false);
    }

    /**
     * @dev Variant of {safeTransferFrom} that returns a bool instead of reverting if the operation is not successful.
     */
    function trySafeTransferFrom(IERC20 token, address from, address to, uint256 value) internal returns (bool) {
        return _safeTransferFrom(token, from, to, value, false);
    }

    /**
     * @dev Increase the calling contract's allowance toward `spender` by `value`. If `token` returns no value,
     * non-reverting calls are assumed to be successful.
     *
     * IMPORTANT: If the token implements ERC-7674 (ERC-20 with temporary allowance), and if the "client"
     * smart contract uses ERC-7674 to set temporary allowances, then the "client" smart contract should avoid using
     * this function. Performing a {safeIncreaseAllowance} or {safeDecreaseAllowance} operation on a token contract
     * that has a non-zero temporary allowance (for that particular owner-spender) will result in unexpected behavior.
     */
    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 oldAllowance = token.allowance(address(this), spender);
        forceApprove(token, spender, oldAllowance + value);
    }

    /**
     * @dev Decrease the calling contract's allowance toward `spender` by `requestedDecrease`. If `token` returns no
     * value, non-reverting calls are assumed to be successful.
     *
     * IMPORTANT: If the token implements ERC-7674 (ERC-20 with temporary allowance), and if the "client"
     * smart contract uses ERC-7674 to set temporary allowances, then the "client" smart contract should avoid using
     * this function. Performing a {safeIncreaseAllowance} or {safeDecreaseAllowance} operation on a token contract
     * that has a non-zero temporary allowance (for that particular owner-spender) will result in unexpected behavior.
     */
    function safeDecreaseAllowance(IERC20 token, address spender, uint256 requestedDecrease) internal {
        unchecked {
            uint256 currentAllowance = token.allowance(address(this), spender);
            if (currentAllowance < requestedDecrease) {
                revert SafeERC20FailedDecreaseAllowance(spender, currentAllowance, requestedDecrease);
            }
            forceApprove(token, spender, currentAllowance - requestedDecrease);
        }
    }

    /**
     * @dev Set the calling contract's allowance toward `spender` to `value`. If `token` returns no value,
     * non-reverting calls are assumed to be successful. Meant to be used with tokens that require the approval
     * to be set to zero before setting it to a non-zero value, such as USDT.
     *
     * NOTE: If the token implements ERC-7674, this function will not modify any temporary allowance. This function
     * only sets the "standard" allowance. Any temporary allowance will remain active, in addition to the value being
     * set here.
     */
    function forceApprove(IERC20 token, address spender, uint256 value) internal {
        if (!_safeApprove(token, spender, value, false)) {
            if (!_safeApprove(token, spender, 0, true)) revert SafeERC20FailedOperation(address(token));
            if (!_safeApprove(token, spender, value, true)) revert SafeERC20FailedOperation(address(token));
        }
    }

    /**
     * @dev Performs an {ERC1363} transferAndCall, with a fallback to the simple {ERC20} transfer if the target has no
     * code. This can be used to implement an {ERC721}-like safe transfer that relies on {ERC1363} checks when
     * targeting contracts.
     *
     * Reverts if the returned value is other than `true`.
     */
    function transferAndCallRelaxed(IERC1363 token, address to, uint256 value, bytes memory data) internal {
        if (to.code.length == 0) {
            safeTransfer(token, to, value);
        } else if (!token.transferAndCall(to, value, data)) {
            revert SafeERC20FailedOperation(address(token));
        }
    }

    /**
     * @dev Performs an {ERC1363} transferFromAndCall, with a fallback to the simple {ERC20} transferFrom if the target
     * has no code. This can be used to implement an {ERC721}-like safe transfer that relies on {ERC1363} checks when
     * targeting contracts.
     *
     * Reverts if the returned value is other than `true`.
     */
    function transferFromAndCallRelaxed(
        IERC1363 token,
        address from,
        address to,
        uint256 value,
        bytes memory data
    ) internal {
        if (to.code.length == 0) {
            safeTransferFrom(token, from, to, value);
        } else if (!token.transferFromAndCall(from, to, value, data)) {
            revert SafeERC20FailedOperation(address(token));
        }
    }

    /**
     * @dev Performs an {ERC1363} approveAndCall, with a fallback to the simple {ERC20} approve if the target has no
     * code. This can be used to implement an {ERC721}-like safe transfer that rely on {ERC1363} checks when
     * targeting contracts.
     *
     * NOTE: When the recipient address (`to`) has no code (i.e. is an EOA), this function behaves as {forceApprove}.
     * Oppositely, when the recipient address (`to`) has code, this function only attempts to call {ERC1363-approveAndCall}
     * once without retrying, and relies on the returned value to be true.
     *
     * Reverts if the returned value is other than `true`.
     */
    function approveAndCallRelaxed(IERC1363 token, address to, uint256 value, bytes memory data) internal {
        if (to.code.length == 0) {
            forceApprove(token, to, value);
        } else if (!token.approveAndCall(to, value, data)) {
            revert SafeERC20FailedOperation(address(token));
        }
    }

    /**
     * @dev Imitates a Solidity `token.transfer(to, value)` call, relaxing the requirement on the return value: the
     * return value is optional (but if data is returned, it must not be false).
     *
     * @param token The token targeted by the call.
     * @param to The recipient of the tokens
     * @param value The amount of token to transfer
     * @param bubble Behavior switch if the transfer call reverts: bubble the revert reason or return a false boolean.
     */
    function _safeTransfer(IERC20 token, address to, uint256 value, bool bubble) private returns (bool success) {
        bytes4 selector = IERC20.transfer.selector;

        assembly ("memory-safe") {
            let fmp := mload(0x40)
            mstore(0x00, selector)
            mstore(0x04, and(to, shr(96, not(0))))
            mstore(0x24, value)
            success := call(gas(), token, 0, 0x00, 0x44, 0x00, 0x20)
            // if call success and return is true, all is good.
            // otherwise (not success or return is not true), we need to perform further checks
            if iszero(and(success, eq(mload(0x00), 1))) {
                // if the call was a failure and bubble is enabled, bubble the error
                if and(iszero(success), bubble) {
                    returndatacopy(fmp, 0x00, returndatasize())
                    revert(fmp, returndatasize())
                }
                // if the return value is not true, then the call is only successful if:
                // - the token address has code
                // - the returndata is empty
                success := and(success, and(iszero(returndatasize()), gt(extcodesize(token), 0)))
            }
            mstore(0x40, fmp)
        }
    }

    /**
     * @dev Imitates a Solidity `token.transferFrom(from, to, value)` call, relaxing the requirement on the return
     * value: the return value is optional (but if data is returned, it must not be false).
     *
     * @param token The token targeted by the call.
     * @param from The sender of the tokens
     * @param to The recipient of the tokens
     * @param value The amount of token to transfer
     * @param bubble Behavior switch if the transfer call reverts: bubble the revert reason or return a false boolean.
     */
    function _safeTransferFrom(
        IERC20 token,
        address from,
        address to,
        uint256 value,
        bool bubble
    ) private returns (bool success) {
        bytes4 selector = IERC20.transferFrom.selector;

        assembly ("memory-safe") {
            let fmp := mload(0x40)
            mstore(0x00, selector)
            mstore(0x04, and(from, shr(96, not(0))))
            mstore(0x24, and(to, shr(96, not(0))))
            mstore(0x44, value)
            success := call(gas(), token, 0, 0x00, 0x64, 0x00, 0x20)
            // if call success and return is true, all is good.
            // otherwise (not success or return is not true), we need to perform further checks
            if iszero(and(success, eq(mload(0x00), 1))) {
                // if the call was a failure and bubble is enabled, bubble the error
                if and(iszero(success), bubble) {
                    returndatacopy(fmp, 0x00, returndatasize())
                    revert(fmp, returndatasize())
                }
                // if the return value is not true, then the call is only successful if:
                // - the token address has code
                // - the returndata is empty
                success := and(success, and(iszero(returndatasize()), gt(extcodesize(token), 0)))
            }
            mstore(0x40, fmp)
            mstore(0x60, 0)
        }
    }

    /**
     * @dev Imitates a Solidity `token.approve(spender, value)` call, relaxing the requirement on the return value:
     * the return value is optional (but if data is returned, it must not be false).
     *
     * @param token The token targeted by the call.
     * @param spender The spender of the tokens
     * @param value The amount of token to transfer
     * @param bubble Behavior switch if the transfer call reverts: bubble the revert reason or return a false boolean.
     */
    function _safeApprove(IERC20 token, address spender, uint256 value, bool bubble) private returns (bool success) {
        bytes4 selector = IERC20.approve.selector;

        assembly ("memory-safe") {
            let fmp := mload(0x40)
            mstore(0x00, selector)
            mstore(0x04, and(spender, shr(96, not(0))))
            mstore(0x24, value)
            success := call(gas(), token, 0, 0x00, 0x44, 0x00, 0x20)
            // if call success and return is true, all is good.
            // otherwise (not success or return is not true), we need to perform further checks
            if iszero(and(success, eq(mload(0x00), 1))) {
                // if the call was a failure and bubble is enabled, bubble the error
                if and(iszero(success), bubble) {
                    returndatacopy(fmp, 0x00, returndatasize())
                    revert(fmp, returndatasize())
                }
                // if the return value is not true, then the call is only successful if:
                // - the token address has code
                // - the returndata is empty
                success := and(success, and(iszero(returndatasize()), gt(extcodesize(token), 0)))
            }
            mstore(0x40, fmp)
        }
    }
}
          

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.4.0) (token/ERC20/IERC20.sol)

pragma solidity >=0.4.16;

/**
 * @dev Interface of the ERC-20 standard as defined in the ERC.
 */
interface IERC20 {
    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);

    /**
     * @dev Returns the value of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the value of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves a `value` amount of tokens from the caller's account to `to`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address to, uint256 value) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets a `value` amount of tokens as the allowance of `spender` over the
     * caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 value) external returns (bool);

    /**
     * @dev Moves a `value` amount of tokens from `from` to `to` using the
     * allowance mechanism. `value` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address from, address to, uint256 value) external returns (bool);
}
          

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.4.0) (interfaces/IERC20.sol)

pragma solidity >=0.4.16;

import {IERC20} from "../token/ERC20/IERC20.sol";
          

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.4.0) (interfaces/IERC165.sol)

pragma solidity >=0.4.16;

import {IERC165} from "../utils/introspection/IERC165.sol";
          

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.4.0) (interfaces/IERC1363.sol)

pragma solidity >=0.6.2;

import {IERC20} from "./IERC20.sol";
import {IERC165} from "./IERC165.sol";

/**
 * @title IERC1363
 * @dev Interface of the ERC-1363 standard as defined in the https://eips.ethereum.org/EIPS/eip-1363[ERC-1363].
 *
 * Defines an extension interface for ERC-20 tokens that supports executing code on a recipient contract
 * after `transfer` or `transferFrom`, or code on a spender contract after `approve`, in a single transaction.
 */
interface IERC1363 is IERC20, IERC165 {
    /*
     * Note: the ERC-165 identifier for this interface is 0xb0202a11.
     * 0xb0202a11 ===
     *   bytes4(keccak256('transferAndCall(address,uint256)')) ^
     *   bytes4(keccak256('transferAndCall(address,uint256,bytes)')) ^
     *   bytes4(keccak256('transferFromAndCall(address,address,uint256)')) ^
     *   bytes4(keccak256('transferFromAndCall(address,address,uint256,bytes)')) ^
     *   bytes4(keccak256('approveAndCall(address,uint256)')) ^
     *   bytes4(keccak256('approveAndCall(address,uint256,bytes)'))
     */

    /**
     * @dev Moves a `value` amount of tokens from the caller's account to `to`
     * and then calls {IERC1363Receiver-onTransferReceived} on `to`.
     * @param to The address which you want to transfer to.
     * @param value The amount of tokens to be transferred.
     * @return A boolean value indicating whether the operation succeeded unless throwing.
     */
    function transferAndCall(address to, uint256 value) external returns (bool);

    /**
     * @dev Moves a `value` amount of tokens from the caller's account to `to`
     * and then calls {IERC1363Receiver-onTransferReceived} on `to`.
     * @param to The address which you want to transfer to.
     * @param value The amount of tokens to be transferred.
     * @param data Additional data with no specified format, sent in call to `to`.
     * @return A boolean value indicating whether the operation succeeded unless throwing.
     */
    function transferAndCall(address to, uint256 value, bytes calldata data) external returns (bool);

    /**
     * @dev Moves a `value` amount of tokens from `from` to `to` using the allowance mechanism
     * and then calls {IERC1363Receiver-onTransferReceived} on `to`.
     * @param from The address which you want to send tokens from.
     * @param to The address which you want to transfer to.
     * @param value The amount of tokens to be transferred.
     * @return A boolean value indicating whether the operation succeeded unless throwing.
     */
    function transferFromAndCall(address from, address to, uint256 value) external returns (bool);

    /**
     * @dev Moves a `value` amount of tokens from `from` to `to` using the allowance mechanism
     * and then calls {IERC1363Receiver-onTransferReceived} on `to`.
     * @param from The address which you want to send tokens from.
     * @param to The address which you want to transfer to.
     * @param value The amount of tokens to be transferred.
     * @param data Additional data with no specified format, sent in call to `to`.
     * @return A boolean value indicating whether the operation succeeded unless throwing.
     */
    function transferFromAndCall(address from, address to, uint256 value, bytes calldata data) external returns (bool);

    /**
     * @dev Sets a `value` amount of tokens as the allowance of `spender` over the
     * caller's tokens and then calls {IERC1363Spender-onApprovalReceived} on `spender`.
     * @param spender The address which will spend the funds.
     * @param value The amount of tokens to be spent.
     * @return A boolean value indicating whether the operation succeeded unless throwing.
     */
    function approveAndCall(address spender, uint256 value) external returns (bool);

    /**
     * @dev Sets a `value` amount of tokens as the allowance of `spender` over the
     * caller's tokens and then calls {IERC1363Spender-onApprovalReceived} on `spender`.
     * @param spender The address which will spend the funds.
     * @param value The amount of tokens to be spent.
     * @param data Additional data with no specified format, sent in call to `spender`.
     * @return A boolean value indicating whether the operation succeeded unless throwing.
     */
    function approveAndCall(address spender, uint256 value, bytes calldata data) external returns (bool);
}
          

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.1.0) (access/Ownable2Step.sol)

pragma solidity ^0.8.20;

import {Ownable} from "./Ownable.sol";

/**
 * @dev Contract module which provides access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * This extension of the {Ownable} contract includes a two-step mechanism to transfer
 * ownership, where the new owner must call {acceptOwnership} in order to replace the
 * old one. This can help prevent common mistakes, such as transfers of ownership to
 * incorrect accounts, or to contracts that are unable to interact with the
 * permission system.
 *
 * The initial owner is specified at deployment time in the constructor for `Ownable`. This
 * can later be changed with {transferOwnership} and {acceptOwnership}.
 *
 * This module is used through inheritance. It will make available all functions
 * from parent (Ownable).
 */
abstract contract Ownable2Step is Ownable {
    address private _pendingOwner;

    event OwnershipTransferStarted(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Returns the address of the pending owner.
     */
    function pendingOwner() public view virtual returns (address) {
        return _pendingOwner;
    }

    /**
     * @dev Starts the ownership transfer of the contract to a new account. Replaces the pending transfer if there is one.
     * Can only be called by the current owner.
     *
     * Setting `newOwner` to the zero address is allowed; this can be used to cancel an initiated ownership transfer.
     */
    function transferOwnership(address newOwner) public virtual override onlyOwner {
        _pendingOwner = newOwner;
        emit OwnershipTransferStarted(owner(), newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`) and deletes any pending owner.
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual override {
        delete _pendingOwner;
        super._transferOwnership(newOwner);
    }

    /**
     * @dev The new owner accepts the ownership transfer.
     */
    function acceptOwnership() public virtual {
        address sender = _msgSender();
        if (pendingOwner() != sender) {
            revert OwnableUnauthorizedAccount(sender);
        }
        _transferOwnership(sender);
    }
}
          

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.0.0) (access/Ownable.sol)

pragma solidity ^0.8.20;

import {Context} from "../utils/Context.sol";

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * The initial owner is set to the address provided by the deployer. This can
 * later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    /**
     * @dev The caller account is not authorized to perform an operation.
     */
    error OwnableUnauthorizedAccount(address account);

    /**
     * @dev The owner is not a valid owner account. (eg. `address(0)`)
     */
    error OwnableInvalidOwner(address owner);

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the address provided by the deployer as the initial owner.
     */
    constructor(address initialOwner) {
        if (initialOwner == address(0)) {
            revert OwnableInvalidOwner(address(0));
        }
        _transferOwnership(initialOwner);
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        if (owner() != _msgSender()) {
            revert OwnableUnauthorizedAccount(_msgSender());
        }
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby disabling any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        if (newOwner == address(0)) {
            revert OwnableInvalidOwner(address(0));
        }
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}